UPDATE — Multiplayer is live (online, with room codes)
Summary
Blackhole.io is now real online multiplayer. Create a room, share the code, and someone on another device joins and you can actually eat each other. Not bots — real people.
Breakdown

moved the whole game simulation onto a server so it’s authoritative (server decides what’s real, clients can’t cheat)

clients now only send their mouse target; the server sends back everyone’s positions

create/join a room with a short code, each room is its own isolated game

added interpolation so other players move smoothly instead of teleporting between updates

bots still fill empty rooms so it’s never a dead lobby

deployed the server to Render and the game page to GitHub Pages, wired together over WebSockets

What fought me
The networking logic wasn’t even the hard part — deploying it was. Getting the GitHub Pages page to actually talk to the Render server took forever. The site kept opening my README instead of the game, the WebSocket wouldn’t connect because it was still pointing at localhost, and it had to be wss:// not ws:// or the browser silently blocked it. Bunch of small things that each looked like the whole thing was broken. Once the client finally connected to the live server and I saw a second black hole move on my screen, that was the moment.

Note: Server May Take some time to start up